Semiconductor device and manufacturing method of the semiconductor device

ABSTRACT

A semiconductor device includes a semiconductor layer formed on an insulating layer; a gate electrode disposed on said semiconductor layer via a gate insulating film; a source/drain layer composed by including an alloy layer or a metal layer with a bottom surface in contact with the insulating layer, with joint surfaces to a channel region disposed along crystal orientation faces of said semiconductor layer; and impurity-doped layers formed in a self-aligned manner along interfaces of the alloy layer or the metal layer, and said semiconductor layer.

This is a Divisional of application Ser. No. 11/446,393 filed Jun. 5,2006. This application claims the benefit of Japanese Patent ApplicationNo. 2005-169631, filed on Jun. 9, 2005. The entire disclosures of theprior applications are hereby incorporated by reference herein in theirentirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a semiconductor device and amanufacturing method of the semiconductor device, and particularly ispreferable for application in a field-effect transistor reduced to asubmicron order or less.

2. Description of the Related Art

In the field-effect transistors of recent years, gate lengths areshortened to a submicron order to promote densification and speedup ofsemiconductor integrated circuits. In order to suppress increase inresistance of source/drain layers of miniaturized field-effecttransistors, silicidation of surfaces of the source/drain layers isperformed.

For example, JP-A-2002-110991 (hereinafter referred to as PatentDocument 1) discloses a method for forming a joint interface of adiffusion layer which is a silicon portion of an SOI layer and a metalsilicide layer to be a (111) silicon plane in order to reduce junctionleakage of the metal silicide layer.

However, when the gate length of a field-effect transistor is reduced toabout 100 nm or less, the control power of channel potential by a gateelectrode reduces, and a leakage current flowing between a source and adrain increases. Therefore, in the field-effect transistor in which thegate length is reduced to about 100 nm or less, it becomes difficult tosuppress a short channel effect sufficiently, thus causing the problemthat a leakage current in an off state of the field-effect transistorincreases.

Further, in the method of siliciding the surfaces of the source/drainlayer, when the silicide layer reaches the joint surfaces of thesource/drain layer and the channel region, junction leakage is caused,and therefore, it is necessary to make the silicide layer thin, thuscausing the problem of making it difficult to contribute to reduction inresistance of the source/drain layer sufficiently.

In the method disclosed in Patent Document 1, there is the problem thatwhen the silicide layer reaches the area in the vicinity of the jointsurfaces of the source/drain layer and the channel region, and when thesilicide reaction proceeds beyond the joint surfaces of the source/drainlayer and the channel region, junction leakage is caused.

SUMMARY

It is an object of the present invention to provide a semiconductordevice in which while junction leakage is suppressed, resistance of asource/drain layer is reduced, and a short channel effect can besuppressed, and a manufacturing method of the semiconductor device.

In order to attain the above-described object, a semiconductor deviceaccording to one aspect of the present invention is characterized byincluding a semiconductor layer formed on an insulating layer, a gateelectrode disposed on the aforesaid semiconductor layer via a gateinsulating film, a source/drain layer composed by including an alloylayer or a metal layer with a bottom surface in contact with theinsulating layer, with joint surfaces to a channel region disposed alongcrystal orientation faces of the aforesaid semiconductor layer, andimpurity-doped layers formed in a self-aligned manner along interfacesof the alloy layer or the metal layer, and the aforesaid semiconductorlayer.

Thereby, it becomes possible to construct the source/drain layer of thealloy layer or the metal layer disposed in all over the depth directionof the semiconductor layer while widening the channel region in thedepth direction, and the thickness of the impurity-doped layers disposedalong the interfaces of the source/drain layer and the semiconductorlayer can be made uniform while flatness of the joint surfaces areenhanced. Therefore, even when the alloy layer or the metal layer isformed so that the bottom surface is in contact with the insulatinglayer, it becomes possible to make the alloy layer or the metal layernot to be in contact with the semiconductor layer being the channelregion, thus making it possible to reduce the resistance of thesource/drain layer while suppressing junction leakage, and to enhancethe energy barrier in the deep region of the channel on which thecontrol by the gate electrode is difficult to exert, and the shortchannel effect can be suppressed.

A semiconductor device according to one aspect of the present inventionis characterized by including a gate electrode disposed on asemiconductor substrate via a gate insulating film, a source/drain layercomposed by including an alloy layer or a metal layer, with jointsurfaces to a channel region disposed along crystal orientation faces ofthe semiconductor substrate, and impurity-doped layers formed in aself-aligned manner along interfaces of the alloy layer or the metallayer and the semiconductor substrate.

Thereby, it becomes possible to thicken the alloy layer or the metallayer composing the source/drain layer while widening the channel regionin the depth direction, and the thickness of the impurity-doped layersdisposed along the interfaces of the source/drain layer and thesemiconductor substrate can be made uniform while flatness of the jointsurfaces to the channel region is enhanced. Therefore, even when thealloy layer or the metal layer is thickened, it becomes possible to keepthe alloy layer or the metal layer from being in contact with thesemiconductor substrate, thus making it possible to reduce theresistance of the source/drain layer while suppressing junction leakageand to enhance the energy barrier of the deep region of the channel onwhich the control by the gate electrode is difficult to exert, and theshort channel effect can be suppressed.

A semiconductor device according to one aspect of the present inventionis characterized by including a semiconductor layer formed on aninsulating layer, a gate electrode disposed on the aforesaidsemiconductor layer via a gate insulating film, and a source/drain layercomposed of a metal layer with a bottom surface in contact with theinsulating layer, with joint surfaces to a channel region disposed alongcrystal orientation faces of the aforesaid semiconductor layer.

Thereby, it becomes possible to compose the source/drain layer of themetal film disposed in all over the depth direction of the semiconductorlayer while widening the channel region in the depth direction.Therefore, it becomes possible to reduce the resistance of thesource/drain layer and to enhance the energy barrier in the deep regionof the channel on which the control by the gate electrode is difficultto exert, and a short channel effect can be suppressed.

A semiconductor device according to one aspect of the present inventionis characterized by including a gate electrode disposed on asemiconductor substrate via a gate insulating film, and a source/drainlayer composed of a metal layer with joint surfaces to a channel regiondisposed along crystal orientation faces of the semiconductor substrate.

Thereby, it becomes possible to thicken the metal layer composing thesource/drain layer while widening the channel region in the depthdirection. Therefore, it becomes possible to reduce the resistance ofthe source/drain layer and to enhance the energy barrier in the deepregion of the channel on which the control by the gate electrode isdifficult to exert, and a short channel effect can be suppressed.

A semiconductor device according to one aspect of the present inventionis characterized in that the crystal orientation faces are (111) planes.

Thereby, it becomes possible to widen the channel region in the depthdirection while securing flatness of the joint surfaces of thesource/drain layer and the channel region, and the crystal orientationfaces being the boundaries of the channel region can be exposed withoutdamaging to the channel region.

A manufacturing method of a semiconductor device according to one aspectof the present invention is characterized by including the steps offorming a gate electrode above a semiconductor layer, forming asource/drain layer composed by including an alloy layer or a metal layerjoined to a channel region of the semiconductor layer, introducing animpurity into the alloy layer or the metal layer, by expelling theimpurity introduced into the alloy layer or the metal layer to thesemiconductor layer side, forming impurity-doped layers disposed atinterfaces of the alloy layer or the metal layer and the semiconductorlayer.

Thereby, the impurity-doped layers can be formed by diffusing theimpurity expelled from the alloy layer or the metal layer to thesemiconductor layer side, and it becomes possible to dispose theimpurity-doped layers in a self-aligned manner along the interfaces ofthe alloy layer or the metal layer and the semiconductor layer.Therefore, even when the alloy layer or the metal layer is formed sothat the bottom surfaces are in contact with the insulating layer, itbecomes possible to keep the alloy layer or the metal layer from beingin contact with the semiconductor layer being the channel region, and itbecomes possible to reduce the resistance of the source/drain layerwhile suppressing the junction leakage. Further, by diffusing theimpurity to the semiconductor layer side via the alloy layer or themetal layer, the temperature necessary for introducing the impurity tothe semiconductor side can be lowered, thus making it possible to reducedamage to the metal gate and the high dielectric constant insulatingfilm, and making it unnecessary to perform ion-implantation directlyinto the semiconductor layer for introducing the impurity into thesemiconductor layer, and the crystal defect occurring to the channelregion can be reduced.

A manufacturing method of a semiconductor device according to one aspectof the present invention is characterized by including the steps offorming a dummy gate electrode above a semiconductor layer, forming asource/drain layer composed by including an alloy layer or a metal layerjoined to a channel region of the semiconductor layer, introducing animpurity into the alloy layer or the metal layer, by expelling theimpurity introduced into the alloy layer or the metal layer to thesemiconductor layer side, forming impurity-doped layers disposed atinterfaces of the alloy layer or the metal layer and the semiconductorlayer, forming an insulating layer in which the dummy gate electrode isburied on the semiconductor layer, forming a trench corresponding to thedummy gate electrode in the insulating layer by removing the dummy gateelectrode buried in the insulating layer, and burying the gate electrodeinto the trench.

Thereby, it becomes possible to form the gate electrode after formingthe impurity-doped layer while keeping self alignment property of thedisposing position of the gate electrode with respect to theimpurity-doped layers. Therefore, the thermal load necessary to form theimpurity-doped layers and the like is prevented from being exerted onthe gate electrode, and it becomes possible to facilitate metallizationof the gate electrode.

A manufacturing method of a semiconductor device according to one aspectof the present invention is characterized by including the steps offorming a gate electrode above a semiconductor layer disposed on aninsulating layer, forming side walls at side walls of the gateelectrode, forming a metal film on an entire surface on thesemiconductor layer on which the side walls are formed, by reacting themetal film with the semiconductor layer by first thermal treatment,forming an alloy layer disposed at sides of the side walls, removing anunreacted metal film at a time of forming the alloy layer, introducingan impurity into the alloy layer, and by causing a bottom surface of thealloy layer to be in contact with the insulating layer by second thermaltreatment, forming a source/drain layer composed of the alloy layer withjoint surfaces disposed along crystal orientation faces of thesemiconductor layer, and by diffusing the impurity introduced into thealloy layer to the semiconductor layer side, forming impurity-dopedlayers disposed at interfaces of the source/drain layer and thesemiconductor layer.

Thereby, it becomes possible to compose the source/drain layer of thealloy layer disposed in all over the depth direction of thesemiconductor layer while widening the channel region in the depthdirection, the impurity-doped layers can be formed by diffusing theimpurity expelled from the alloy layer to the semiconductor layer side,thus making it possible to dispose the impurity-doped layers in theself-aligned manner along the interfaces of the alloy layer and thesemiconductor layer. Therefore, even when the alloy layer is formed sothat the bottom surface is in contact with the insulation layer, itbecomes possible to keep the alloy layer from being in contact with thesemiconductor layer being the channel region. Thus, it becomes possibleto reduce the resistance of the source/drain layer while suppressing thejunction leakage, and the energy barrier in the deep region of thechannel on which the control by the gate electrode is difficult to exertcan be enhanced, thus making it possible to suppress a short channeleffect.

A manufacturing method of a semiconductor device according to one aspectof the present invention is characterized by including the steps offorming a gate electrode above a semiconductor substrate, forming sidewalls at side walls of the gate electrode, forming a metal film on anentire surface on the semiconductor substrate on which the side wallsare formed, by reacting the metal film and the semiconductor substrateby first thermal treatment, forming alloy layers disposed at sides ofthe side walls, removing an unreacted metal film at a time of formingthe alloy layers, introducing an impurity into the alloy layers, andforming a source/drain layer composed of alloy layers with jointsurfaces to a channel region disposed along crystal orientation faces ofthe semiconductor layer by second thermal treatment, diffusing theimpurity introduced into the alloy layers to the semiconductor substrateside, and forming impurity-doped layers disposed at interfaces of thesource/drain layer and the semiconductor substrate.

Thereby, it becomes possible to thicken the alloy layer composing thesource/drain layer while widening the channel region in the depthdirection, and the impurity-doped layer can be formed by diffusing theimpurity expelled from the alloy layer to the semiconductor substrateside, thus making it possible to dispose the impurity-doped layers inthe self-aligned manner along the interfaces of the alloy layer and thesemiconductor substrate. Therefore, even when the alloy layer isthickened, it becomes possible to keep the alloy layer from being incontact with the semiconductor substrate being the channel region, andit becomes possible to reduce the resistance of the source/drain layerwhile suppressing the junction leakage, thus making it possible toenhance the energy barrier in the deep region of the channel on whichthe control of the gate electrode is difficult to exert, and to suppressa short channel effect.

A manufacturing method of a semiconductor device according to one aspectof the present invention is characterized by including the steps offorming a gate electrode above a semiconductor layer disposed on aninsulating layer, forming side walls at side walls of the gateelectrode, by etching the semiconductor layer with the gate electrodeand the side walls as a mask, exposing inclined surfaces of thesemiconductor layer along crystal orientation faces, forming a metalfilm or an alloy film on an entire surface on the insulating layer sothat the exposed inclined surfaces are covered with the metal film orthe alloy film, by removing the metal film or the alloy film on the gateelectrode, forming a source/drain layer composed of the metal film orthe alloy film joined to the semiconductor layer via the crystalorientation faces.

Thereby, it becomes possible to compose the source/drain layer of themetal film or the alloy film disposed in all over the entire depthdirection of the semiconductor layer while widening the channel regionin the depth direction, and it is not necessary to react the metal withthe semiconductor layer to compose the source/drain layer of the metalfilm or the alloy film. Therefore, even when the source/drain layer iscomposed of the metal film or the alloy film, it becomes possible toincrease the choices of the kind of the metal film or the alloy film,and it becomes possible to stabilize the composition of the metal filmor the alloy film, thus making it possible to reduce the resistance ofthe source/drain layer and to suppress a short channel effect.

A manufacturing method of a semiconductor device according to one aspectof the present invention is characterized by further including the stepsof introducing an impurity into the metal film or the alloy layer, andby diffusing the impurity introduced into the metal film or the alloylayer to the semiconductor layer side, forming impurity-doped layersdisposed at interfaces of the source/drain layer and the semiconductorlayer.

Thereby, the impurity-doped layer can be formed by diffusing theimpurity expelled from the metal film or the alloy film to thesemiconductor layer side, and it becomes possible to dispose theimpurity-doped layer in the self-aligned manner along the interfaces ofthe metal film or the alloy film and the semiconductor layer. Therefore,even when the metal film or the alloy layer is formed so that the bottomsurface is in contact with the insulating layer, it becomes possible tokeep the metal film or the alloy layer from being in contact with thesemiconductor layer being the channel region, and it becomes possible toreduce the resistance of the source/drain layer while suppressing thejunction leakage.

A manufacturing method of a semiconductor device according to one aspectof the present invention is characterized by including the steps offorming a gate electrode above a semiconductor substrate, forming sidewalls at side walls of the gate electrode, by etching the semiconductorsubstrate with the gate electrode and the side walls as a mask, exposinginclined surfaces of the semiconductor substrate along crystalorientation faces of the semiconductor substrate, forming a metal filmor an alloy film on an entire surface on the semiconductor substrate sothat the exposed inclined surfaces are covered with the metal film orthe alloy film, by removing the metal film or the alloy film on the gateelectrode, forming a source/drain layer composed of the metal film orthe alloy film joined to the semiconductor substrate via the crystalorientation faces.

Thereby, it becomes possible to thicken the metal film or the alloylayer composing the source/drain layer while widening the channel regionin the depth direction, and since the source/drain layer is composed ofthe metal film or the alloy film, it is not necessary to react the metalwith the semiconductor substrate. Therefore, it becomes possible toreduce the resistance of the source/drain layer, and a short channeleffect can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a schematic construction of asemiconductor device according to a first embodiment of the presentinvention;

FIG. 2 is a view showing a schematic construction of a semiconductordevice according to a second embodiment of the present invention;

FIGS. 3A and 3B are views showing schematic constructions of asemiconductor device according to a third embodiment of the presentinvention;

FIG. 4 is a view of a schematic construction of a semiconductor deviceaccording to a fourth embodiment of the present invention;

FIGS. 5A to 5D are diagrams showing simulation results ofcharacteristics of the semiconductor device according to one embodimentof the present invention by being compared with the prior art;

FIG. 6 is a diagram showing V_(G)-I_(D) and I_(G) characteristics of thesemiconductor device according to one embodiment of the presentinvention;

FIGS. 7A to 7E are sectional views showing a manufacturing method of asemiconductor device according to a fifth embodiment of the presentinvention;

FIGS. 8A to 8C are sectional views showing a manufacturing method of asemiconductor device according to a sixth embodiment of the presentinvention; and

FIGS. 9A to 9F are sectional views showing a manufacturing method of asemiconductor device according to a seventh embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a semiconductor device and its manufacturing methodaccording to embodiments of the present invention will be described withreference to the drawings.

FIG. 1 is a sectional view showing a schematic construction of asemiconductor device according to a first embodiment of the presentinvention.

In FIG. 1, an insulating layer 12 is formed on a supporting substrate11, and a monocrystal semiconductor layer 13 is formed on the insulatinglayer 12. As the supporting substrate 11, a semiconductor substrate ofSi, Ge, SiGe, GaAs, InP, GaP, GaN, SiC or the like may be used, or aninsulating substrate of glass, sapphire, ceramics or the like may beused. As the material of the monocrystal semiconductor layer 13, forexample, Si, Ge, SiGe, SiC, SiSn, PbS, GaAs, InP, GaP, GaN, ZnSe or thelike can be used, and as the insulating layer 12, an insulating layer ora buried insulating film of, for example, SIO₂, SiON, Si₃N₄ or the likecan be used. As the semiconductor substrate with the monocrystalsemiconductor layer 13 formed on the insulating layer 12, for example,an SOI substrate can be used, and as the SOI substrate, an SIMOX(Separation by Implanted Oxygen) substrate, a bonded substrate, a laseranneal substrate or the like can be used. Instead of the monocrystalsemiconductor layer 13, a polycrystalline semiconductor layer or anamorphous semiconductor layer may be used.

A gate electrode 15 is disposed on the monocrystal semiconductor layer13 via a gate insulating film 14. As a material of the gate insulatingfilm 14, a dielectric of, for example, HfO₂, HfON, HfAlO, HfAlON, HfSiO,HfSiON, ZrO₂, ZrON, ZrAlO, ZrAlON, ZrSiO, ZrSiON, Ta₂O₅, Y₂O₃, (Sr, Ba)TiO₃, LaAlO₃, SrBi₂Ta₂O₉, Bi₄Ti₃O₁₂, Pb (Zi, Ti) O₃ or the like may beused other than SiO₂. As the material of the gate electrode 15, forexample, a metal material of TaN, TiN, W, Pt, Cu or the like may be usedother than polycrystalline silicon. The gate length of the gateelectrode 15 is preferably set at 100 nm or less.

A side wall 16 a is formed at one side wall of the gate electrode 15,and a side wall 16 b is formed at the other side wall of the gateelectrode 15. At one side of the gate electrode 15, a source layer 18 aformed of an alloy layer with its bottom surface in contact with theinsulating layer 12 is disposed. Here, in the alloy layer composing thesource layer 18 a, a joint surface to a channel region 17 is formedalong a crystal orientation face 20 a of the monocrystal semiconductorlayer 13. At the other side of the gate electrode 15, a drain layer 18 bformed of an alloy layer with its bottom surface in contact with theinsulating layer 12 is disposed. Here, in the alloy layer composing thedrain layer 18 b, a joint surface to the channel region 17 is formedalong a crystal orientation face 20 b of the monocrystal semiconductorlayer 13.

The alloy layer can be formed by reacting metal with the monocrystalsubstrate layer 13. When the monocrystal semiconductor layer 13 isformed of monocrystal Si, silicide can be used, when the monocrystalsemiconductor layer 13 is formed of monocrystal SiGe, germanosilicidecan be used, and when the monocrystal semiconductor layer 13 is formedof monocrystal Ge, germanoide can be used. Metal included in the alloylayer can be alloyed by being reacted with the monocrystal semiconductorlayer 13, and for example, Ti, Co, W, Mo, Ni, Pt or the like can beused. Here, it is preferable to select the alloy layer having a latticeconstant close to that of the monocrystal semiconductor layer 13, and itis preferable that the difference between the lattice constants of thealloy layer and the monocrystal semiconductor layer 13 is within 1%. Thecrystal orientation faces 20 a and 20 b can be, for example, (111)planes of the monocrystal semiconductor layer 13.

An impurity-doped layer 19 a formed in a self-aligned manner to be alongthe crystal orientation face 20 a is provided at an interface of thealloy layer composing the source layer 18 a and the monocrystalsemiconductor layer 13. Further, an impurity-doped layer 19 b formed ina self-aligned manner to be along the crystal orientation face 20 b isprovided at an interface of the alloy layer composing the drain layer 18b and the monocrystal semiconductor layer 13. The impurity-doped layers19 a and 19 b can be doped in a high concentration so that an energybarrier does not occur between the impurity-doped layers 19 a and 19 band the alloy layers composing the source layer 18 a and the drain layer18 b.

Thereby, it becomes possible to compose the source layer 18 a and thedrain layer 18 b of the alloy layers disposed in all over the depthdirection of the monocrystal semiconductor layer 13 while widening thechannel region 17 in the depth direction, and the thickness of theimpurity-doped layers 19 a and 19 b disposed along the interface of thealloy layer and the monocrystal semiconductor layer 13 can be madeuniform while flatness of the joint surfaces is enhanced. Therefore,even when the alloy layers are formed for the source layer 18 a and thedrain layer 18 b so that the bottom surfaces are in contact with theinsulating layer 12, it becomes possible for the alloy layer not to bein contact with the monocrystal semiconductor layer 13 being the channelregion, and it becomes possible to reduce resistance of the source layer18 a and the drain layer 18 b while suppressing junction leakage. Inaddition, energy barrier in the deep region of the channel on whichcontrol by the gate electrode 15 is not exerted can be enhanced, and ashort channel effect can be suppressed.

FIG. 2 is a sectional view showing a schematic construction of asemiconductor device according to a second embodiment of the presentinvention.

In FIG. 2, a gate electrode 35 is disposed on a semiconductor substrate31 via a gate insulating film 34. A side wall 36 a is formed at one sidewall of the gate electrode 35, and a side wall 36 b is formed at theother side wall of the gate electrode 35. A source layer 38 a composedof an alloy layer buried in the semiconductor substrate 31 is disposedat one side of the gate electrode 35. Here, in the alloy layer composingthe source layer 38 a, a joint surface to a channel region 37 is formedalong a crystal orientation face 40 a of the semiconductor substrate 31.A drain layer 38 b composed of an alloy layer buried in thesemiconductor substrate 31 is disposed at the other side of the gateelectrode 35. Here, in the alloy layer composing the drain layer 38 b, ajoint surface to the channel region 37 is formed along a crystalorientation face 20 b of the semiconductor substrate 31. When a (100)substrate is used as the semiconductor substrate 31, the crystalorientation faces 40 a and 40 b can be, for example, (111) planes of thesemiconductor substrate 31. When the semiconductor substrate 31 isformed of monocrystal Si, silicide can be used for the alloy layers 38 aand 38 b.

An impurity-doped layer 39 a formed in a self-aligned manner to be alongan interface with the semiconductor substrate 31 is provided at theinterface of the alloy layer composing the source layer 38 a and thesemiconductor substrate 31. An impurity-doped layer 39 b formed in aself-aligned manner to be along an interface with the semiconductorsubstrate 31 is provided at the interface of the alloy layer composingthe drain layer 38 b and the semiconductor substrate 31. Theimpurity-doped layers 39 a and 39 b can be doped in a high concentrationso that an energy barrier does not occur between the impurity-dopedlayers 39 a and 39 b and the alloy layers composing the source layer 38a and the drain layer 38 b.

Thereby, it becomes possible to thicken the alloy layers composing thesource layer 38 a and the drain layer 38 b while widening the channelregion 37 in the depth direction, and the thickness of theimpurity-doped layers 39 a and 39 b disposed along the interface of thealloy layers and the semiconductor substrate 31 can be made uniformwhile flatness of the joint surfaces to the channel region 37 isenhanced. Therefore, even when the alloy layer formed in thesemiconductor substrate 31 is thickened, it becomes possible for thealloy layer not to be in contact with the semiconductor substrate 31being the channel region, and it becomes possible to reduce resistanceof the source layer 38 a and the drain layer 38 b while suppressingjunction leakage. In addition, the energy barrier in the deep region ofthe channel on which the control of the gate electrode 35 is not exertedcan be enhanced, and a short channel effect can be suppressed.

FIG. 3B is a perspective view showing a schematic construction of asemiconductor device according to a third embodiment of the presentinvention, and FIG. 3A is a sectional view which is cut along a P planein FIG. 3B.

In FIGS. 3A and 3B, an insulating layer 52 is formed on a supportingsubstrate 51, and a monocrystal semiconductor layer 53 having a finshape is formed on the insulating layer 52. An insulating layer 61 isformed on the monocrystal semiconductor layer 53, and at side walls atboth sides of the monocrystal semiconductor layer 53, a gate electrode55 disposed to stride over the monocrystal semiconductor layer 53 isformed via a gate insulating film 54. A side wall 56 a is formed at oneside wall of the gate electrode 55, and a side wall 56 b is formed atthe other side wall of the gate electrode 55. At one side of the gateelectrode 55, a source layer 58 a in which the entire monocrystalsemiconductor layer 53 is filled with an alloy layer is disposed. Here,in the alloy layer composing the source layer 58 a, a joint surface to achannel region 57 is formed to widen in the depth direction along acrystal orientation face 60 a of the monocrystal semiconductor layer 53.At the other side of the gate electrode 55, a drain layer 58 b in whichthe entire single crystal semiconductor layer 53 is filled with an alloylayer is disposed. Here, in the alloy layer composing the drain layer 58b, a joint surface to the channel region 57 is formed to widen in thedepth direction along the crystal orientation surface 60 b of themonocrystal semiconductor layer 53. As the alloy layers 58 a and 58 b,silicide can be used when the semiconductor substrate 51 is formed ofmonocrystal Si. The crystal orientation faces 60 a and 60 b can be, forexample, (111) planes of the monocrystal semiconductor layer 53.

An impurity-doped layer 59 a formed in a self-aligned manner to be alongthe crystal orientation face 60 a is provided at an interface of thealloy layer composing the source layer 58 a and the monocrystalsemiconductor layer 53. An impurity-doped layer 59 b formed in aself-aligned manner to be along the crystal orientation face 60 b isprovided at an interface of the alloy layer composing the drain layer 58b and the monocrystal semiconductor layer 53. The impurity-doped layers59 a and 59 b can be doped in a high concentration so that an energybarrier does not occur between the impurity-doped layers 59 a and 59 band the alloy layers composing the source layer 58 a and the drain layer58 b.

Thereby, it becomes possible to control the potential of the channelregion 57 from a plurality of directions while widening the channelregion 57 in the depth direction, and it becomes possible to compose thesource layer 58 a and the drain layer 58 b of the alloy layers disposedin all over the depth direction of the monocrystal semiconductor layer53. Therefore, it becomes possible to reduce resistance of the sourcelayer 58 a and the drain layer 58 b, and the current drive ability canbe enhanced while suppressing a short channel effect.

FIG. 4 is a sectional view showing a schematic construction of asemiconductor device according to a fourth embodiment of the presentinvention.

In FIG. 4, an insulating layer 172 is formed on a supporting substrate171, and a monocrystal semiconductor layer 173 is formed on theinsulating layer 172. A gate electrode 175 is disposed on themonocrystal semiconductor layer 173 via a gate insulating film 174. Atone side wall of the gate electrode 175, a side wall 176 a is formed,and at the other side wall of the gate electrode 175, a side wall 176 bis formed. Atone side of the gate electrode 175, a source layer 178 acomposed of a metal layer with its bottom surface in contact with theinsulating layer 172 is disposed. Here, in the metal layer composing thesource layer 178 a, a joint surface to a channel region 177 is formedalong a crystal orientation face 180 a of the monocrystal semiconductorlayer 173, and schottky junction is performed between the source layer178 a and the monocrystal semiconductor layer 173. A drain layer 178 bcomposed of a metal layer with its bottom surface in contact with theinsulating layer 172 is disposed at the other side of the gate electrode175. Here, in the metal layer composing the drain layer 178 b, a jointsurface to the channel region 177 is formed along the crystalorientation face 180 b of the monocrystal semiconductor layer 173, andschottky junction is performed between the drain layer 178 b and themonocrystal semiconductor layer 173. The crystal orientation faces 180 aand 180 b can be, for example, (111) planes of the monocrystalsemiconductor layer 173. As the metal layers composing the source layer178 a and the drain layer 178 b, for example, TaN, TiN, W, Pt, Cu andthe like can be used.

Thereby, it becomes possible to compose the source layer 178 a and thedrain layer 178 b of the metal layers disposed in all over the depthdirection of the monocrystal semiconductor layer 173 while widening thechannel region 177 in the depth direction. Therefore, it becomespossible to reduce the resistance of the source layer 178 a and thedrain layer 178 b, and the energy barrier in the deep region of thechannel on which control by the gate electrode 175 is difficult to exertcan be enhanced, thus making it possible to suppress a short channeleffect.

An impurity-doped layer formed in a self-aligned manner to be along thecrystal orientation face 180 a may be provided at an interface of thealloy layer composing the source layer 178 a and the monocrystalsemiconductor layer 173. Further, an impurity-doped layer formed in aself-aligned manner to be along the crystal orientation face 180 b maybe provided at an interface of the alloy layer composing the drain layer178 b and the monocrystal semiconductor layer 173. In the constructionin FIG. 4, the explanation is made with the method of using the SOIsubstrate taken as an example, but the present invention may be appliedto the method using a bulk substrate.

FIGS. 5A and 5B are diagrams showing the simulation result of thecharacteristics of the semiconductor device according to one embodimentof the present invention by being compared with the prior art, and FIGS.5C and 5D are sectional views showing the constructions of thesemiconductor devices used for the simulation of FIGS. 5A and 5B. FIG.5A is a diagram showing the simulation result of the potentialdistribution in the channel direction by being compared with the priorart, FIG. 5B is a diagram showing the simulation result of V_(G)-I_(D)characteristics by being compared with the prior art, FIG. 5C is asectional view showing the construction used as the prior art in thesimulation of this time, and FIG. 5D is a sectional view showing theconstruction used as one example of the present invention in thesimulation of this time.

In FIG. 5C, a monocrystal Si layer 73 is formed on a BOX layer 72. Agate electrode 75 is disposed on the monocrystal Si layer 73 via a gateinsulating film 74. A source layer 78 a and a drain layer 78 b composedof nickel disilicide are formed in the monocrystal Si layer 73 so thatthe length of a channel region 77 kept constant in the depth direction.

Meanwhile, in FIG. 5D, a monocrystal Si layer 83 is formed on a BOXlayer 82. A gate electrode 85 is disposed on the monocrystal Si layer 83via a gate insulating film 84. A source layer 88 a and a drain layer 88b composed of nickel disilicide are formed in the monocrystal Si layer83 so that the channel region 77 widens in the depth direction along(111) planes of the monocrystal Si layer 83.

Simulation was performed with film thicknesses Ts of the monocrystal Silayers 73 and 83 set at 10 nm, gate lengths Lg of the gate electrodes 75and 85 set at 20 nm, work functions φ_(M) of the gate electrodes 75 and85 set at 4.6 eV, film thicknesses of the gate insulating films 74 and84 set at 1 nm, surface lengths L1 of the channel regions 77 and 87 bothset at 20 nm, a bottom surface length L2 of the channel region 77 set at20 nm, a bottom surface length L2 of the channel region 87 set at 40 nm,the source layers 78 a and 88 a grounded, and a drain voltage V_(D)=0.6V applied to the drain layers 78 b and 88 b.

As a result, as shown in FIG. 5A, it is found out that in theconstruction of FIG. 5D, control power of the potential at the bottomsurface of the channel region 87 by the gate electrode 85 increases andthe energy barrier at the bottom surface of the channel region 87becomes high as compared with the construction of FIG. 5C.

As shown in FIG. 5B, it is found out that in the construction of FIG.5D, increase in the off current can be suppressed while reduction in theon current is suppressed, as compared with the construction of FIG. 5C.

FIG. 6 is a diagram showing the V_(G)-I_(D) characteristics and theV_(G)-I_(G) characteristics of the semiconductor device according to oneembodiment of the present invention. The characteristics in FIG. 6 aremeasured by experimentally producing the field-effect transistor of theconstruction of FIG. 1. Here, monocrystal Si is used as the monocrystalsemiconductor layer 13, HfAlO_(x) as the material of the gate insulatingfilm 14, and a nickel disilicide gate as the material of the sourcelayer 18 a and the drain layer 18 b, with the gate length of theelectrode 15 set at 8 nm.

In FIG. 6, as the subthreshold slope value, 122 mV/dec. is obtained, andeven when the gate length is set to be short at 8 nm, degradation of thecharacteristics due to the short channel effect can be suppressed.

FIGS. 7A to 7E are sectional views showing one example of amanufacturing method of a semiconductor device according to a fifthembodiment of the present invention.

In FIG. 7A, an insulating layer 102 is formed on a supporting substrate101, and a monocrystal semiconductor layer 103 is formed on theinsulating layer 102. Then, by performing thermal oxidation of thesurface of the monocrystal semiconductor layer 103, a gate insulatingfilm 104 is formed on the surface of the monocrystal semiconductor layer103. Then, a conductor film is formed on the monocrystal semiconductorlayer 103 on which the gate insulating film 104 is formed by the methodsuch as CVD. Then, by patterning the conductor film using thephotolithography technique and etching technique, a gate electrode 105is formed above the monocrystal semiconductor layer 103. Then, by themethod such as CVD, an insulating layer is formed on the entire surfaceon the monocrystal semiconductor layer 103, and by etching back theinsulating layer using anisotropic etching such as RIE, side walls 106 aand 106 b are respectively formed at side walls of the gate electrode105.

Next, as shown in FIG. 7B, by a method such as sputtering, a metal film107 is formed on the monocrystal semiconductor layer 103 on which theside walls 106 a and 106 b are formed. In this case, the metal film 107is capable of being alloyed by reacting with the monocrystalsemiconductor layer 103, and for example, a Ti film, a Co film, a Wfilm, a Mo film, an Ni film, a Pt film or the like can be used.

Next, as shown in FIG. 7C, thermal treatment of the monocrystalsemiconductor layer 103 on which the metal film 107 is formed isperformed, and the monocrystal semiconductor layer 103 is reacted withthe metal film 107, whereby, alloy layers 111 a and 111 b disposed atthe sides of the side walls 106 a and 106 b are formed on themonocrystal semiconductor layer 103. Then, after the alloy layers 111 aand 111 b are formed, wet etching of the metal film 107 is performed,and thereby unreacted metal film 107 is removed.

Next, as shown in FIG. 7D, ion implantation IN1 of an impurity 112 suchas As, P and B is performed with the gate electrode 105 and the sidewalls 106 a and 106 b as a mask, and thereby, the impurity 112 isintroduced into the alloy layers 111 a and 111 b.

Next, as shown in FIG. 7E, thermal treatment of the monocrystalsemiconductor layer 103 is performed with the impurity 112 implantedinto the alloy layers 111 a and 111 b, and thereby, while joint surfacesto the alloy layers 111 a and 111 b are formed respectively alongcrystal orientation surfaces 110 a and 110 b of the monocrystalsemiconductor layer 103, a source layer 108 a and a drain layer 108 bwhich are respectively composed of the alloy layers 111 a and 111 b withtheir bottom surfaces in contact with the insulating layer 102 areformed. When thermal treatment of the monocrystal semiconductor layer103 is performed with the impurity 112 implanted into the alloy layers111 a and 111 b, the impurity 112 implanted into the alloy layers 111 aand 111 b diffuses to the monocrystal semiconductor layer 103 side, andimpurity-doped layers 109 a and 109 b respectively disposed atinterfaces of the source layer 108 a and the drain layer 108 b, and themonocrystal semiconductor layer 103 are formed in a self-aligned manner.

Thereby, it becomes possible to compose the source layer 108 a and thedrain layer 108 b of the alloy layers disposed in all over the depthdirection of the monocrystal semiconductor layer 103 while widening thechannel region 103 in the depth direction, and the impurity-doped layers109 a and 109 b can be formed by diffusing the impurity 112 expelledfrom the alloy layers 111 a and 111 b to the monocrystal semiconductorlayer 103 side, thus making it possible to dispose the impurity-dopedlayers 109 a and 109 b in a self-aligned manner along the interfaces ofthe source layer 108 a and the drain layer 108 b and the monocrystalsemiconductor layer 103. Therefore, even when the alloy layers areformed in the source layer 108 a and the drain layer 108 b so that thebottom surfaces are in contact with the insulating layer 102, it becomespossible to keep the alloy layers from being in contact with themonocrystal semiconductor layer 103 being the channel region, and itbecomes possible to reduce resistance of the source layer 108 a and thedrain layer 108 b while suppressing junction leak, thus making itpossible to enhance the energy barrier in the deep region of the channelon which control by the gate electrode 105 is difficult to exert, andmaking it possible to suppress the short channel effect.

By diffusing the impurity 112 to the monocrystal semiconductor layer 103side via the alloy layers 111 a and 111 b, the temperature necessary tointroduce the impurity 112 to the monocrystal semiconductor layer 103side can be lowered, thus making it possible to reduce a damage to themetal gate and the high dielectric constant insulating film, andeliminating necessity of directly performing the ion implantation IN1 tothe monocrystal semiconductor layer 103 to introduce the impurity 112into the monocrystal semiconductor layer 103, and a crystal defectoccurring to the channel region 103 can be reduced.

FIGS. 8A to 8C are sectional views showing a manufacturing method of asemiconductor device according to a sixth embodiment of the presentinvention.

In FIG. 8A, after the process step of FIG. 7E, an insulating film 113 isdeposited on the entire surface on the monocrystal semiconductor layer103 by a method such as CVD. In the sixth embodiment, a dummy gateelectrode 105′ is formed instead of the gate electrode 105, andthereafter, the process steps in FIGS. 7A to 7E are performed. In thiscase, as the material of the dummy gate electrode 105′, an insulatorsuch as, for example, a silicon oxide film and a silicon nitride filmcan be used. By thinning the insulating film 113 by a method such as CMP(chemical mechanical polishing) or etch back, the surface of the dummygate electrode 105′ is exposed.

Next, as shown in FIG. 8B, the dummy gate electrode 105′ is removed withthe insulating film 113 left on the monocrystal semiconductor layer 103by a method such as wet etching, and a trench 114 with the side walls106 a and 106 b disposed at the side walls is formed in the insulatingfilm 113.

Next, as shown in FIG. 8C, a conductor film disposed to fill the trench114 is formed on the insulating film 113 by a method such as CVD. Then,the conductor film is thinned by a method such as CMP, and thereby, thegate electrode 115 buried in the trench 114 is formed on the monocrystalsemiconductor layer 103.

Thereby, it becomes possible to form the gate electrode 115 afterforming the impurity-doped layers 109 a and 109 b while keeping selfalignment property of the disposing position of the gate electrode 115with respect to the impurity-doped layers 109 a and 109 b. Therefore,thermal load necessary for formation of the impurity-doped layers 109 aand 109 b and the like can be prevented from exerting on the gateelectrode 115, and it becomes possible to facilitate metallization ofthe gate electrode 115.

FIGS. 9A to 9F are sectional views showing a manufacturing method of asemiconductor device according to a seventh embodiment of the presentinvention.

In FIG. 9A, an insulating layer 202 is formed on a supporting substrate201, and a monocrystal semiconductor layer 203 is formed on theinsulating layer 202. Then, by performing thermal oxidation of thesurface of the monocrystal semiconductor layer 203, a gate insulatingfilm 204 is formed on the surface of the monocrystal semiconductor layer203. Then, a conductor film is formed by a method such as CVD on themonocrystal semiconductor layer 203 on which the gate insulating film204 is formed. Then, by patterning the conductor film using thephotolithography technique and the etching technique, a gate electrode205 is formed above the monocrystal semiconductor layer 203, andthereafter, side walls 206 and 206 b are respectively formed at sidewalls of the gate electrode 205.

Next, as shown in FIG. 9B, by performing wet etching for the monocrystalsemiconductor layer 203 with the gate electrode 205, and the side walls206 a and 206 b as a mask, the monocrystal semiconductor layer 203 atboth sides of the gate electrode 205 is removed while inclined surfacesof the monocrystal semiconductor layer 203 are exposed along the crystalorientation faces 210 a and 210 b. The crystal orientation faces 210 aand 210 b can be, for example, (111) planes. As an etching solution forthe monocrystal semiconductor layer 203, for example, KOH and TMAH(Tetra Methyl Ammonium Hydro-oxide) solutions can be used.

Next, as shown in FIG. 9C, by a method such as sputtering, a metal film207 is formed on the insulating layer 202 to cover the crystalorientation faces 210 a and 210 b. In this case, as the metal film 207,for example, TaN, TiN, W, Pt, Cu and the like can be used. Instead ofthe metal film 207, an alloy film such as silicide may be formed on theinsulating film 202.

As shown in FIG. 9D, by flattening the metal film 207 by a method suchas CMP, the metal film 207 on the gate electrode 205 is removed, and asource layer 208 a and a drain layer 208 b composed of the metal film207 with schottky junction to the monocrystal semiconductor layer 203performed via the crystal orientation faces 210 a and 210 b are formed.

Next, as shown in FIG. 9E, by performing ion-implantation IN2 of animpurity 211 such as As, P and B with the gate electrode 205 and theside walls 206 a and 206 b as a mask, the impurity 211 is introducedinto the metal film 207 in the source layer 208 a and the drain layer208 b.

Next, as shown in FIG. 9F, by performing thermal treatment of themonocrystal semiconductor layer 203 with the impurity 211 implanted intothe metal film 207, the impurity 211 implanted into the metal film 207is diffused to the monocrystal semiconductor layer 203 side, andimpurity-doped layers 209 a and 209 b respectively disposed at theinterfaces of the source layer 208 a and the drain layer 208 b and themonocrystal semiconductor layer 203 are formed in a self-aligned manner.

Thereby, it becomes possible to compose the source layer 208 a and thedrain layer 208 b of the metal film or the alloy film disposed in allover the depth direction of the monocrystal semiconductor layer 203,while widening the channel region 203 in the depth direction, and sincethe source layer 208 a and the drain layer 208 b are composed of themetal film or the alloy film, it becomes unnecessary to react metal withthe monocrystal semiconductor layer 203. Therefore, even when the sourcelayer 208 a and the drain layer 208 b are composed of the metal film orthe alloy film, it becomes possible to extend range of choices of thekind of the metal film or the alloy film, and it becomes possible tostabilize the composition of the metal film or the alloy film. Further,it becomes possible to reduce resistance of the source layer 208 a andthe drain layer 208 b, and a short channel effect can be suppressed.

In the embodiment in FIGS. 9A to 9F, the method for forming theimpurity-doped layers 209 a and 209 b at the interfaces of the sourcelayer 208 a and the drain layer 208 b and the monocrystal semiconductorlayer 203 is described, but the impurity-doped layers 209 a and 209 bmay be omitted. Further, in the construction of FIGS. 9A to 9F, theexplanation made with the method for using the SOI substrate isdescribed, but the present invention may be applied to the method usinga bulk substrate.

1. A semiconductor device, comprising: an insulating layer; asemiconductor layer formed on the insulating layer, the semiconductorlayer including a channel region and defining a first crystal face and asecond crystal face; a gate insulating film disposed on thesemiconductor layer; a gate electrode disposed on the gate insulatingfilm; a source layer including a first alloy layer or a first metallayer, and having a bottom surface, the bottom surface of the sourcelayer being in contact with the insulating layer, the source layerdefining a joint surface of the source layer adjacent to the channelregion disposed along the first crystal face of the semiconductor layer;a drain layer including a second alloy layer or a second metal layer,and having a bottom surface, the bottom surface of the drain layer beingin contact with the insulating layer, the drain layer defining a jointsurface of the drain layer adjacent to the channel region disposed alongthe second crystal face of the semiconductor layer; a first impuritydoped layer along an interface of the first alloy layer or the firstmetal layer of the source layer, and the semiconductor layer; and asecond impurity doped layer along an interface of the second alloy layeror the second metal layer of the drain layer, and the semiconductorlayer, the first crystal face and the second crystal face being (111)plane.
 2. A semiconductor device, comprising: a semiconductor substratehaving a channel region and defining a first crystal face and a secondcrystal face; a gate insulating film disposed on the semiconductorsubstrate; a gate electrode disposed on the gate insulating film; asource layer including a first alloy layer or a first metal layer, thesource layer defining a joint surface of the source layer adjacent tothe channel region disposed along the first crystal face of thesemiconductor substrate; a drain layer including a second alloy layer ora second metal layer, the drain layer defining a joint surface of thedrain layer adjacent to the channel region disposed along the secondcrystal face of the semiconductor substrate; a first impurity dopedlayer disposed along an interface of the first alloy layer or the firstmetal layer of the source layer, and the semiconductor substrate; and asecond impurity doped layer disposed along an interface of the secondalloy layer or the second metal layer of the drain layer, and thesemiconductor substrate, the first crystal face and the second crystalface being (111) plane.